After months of stalled contract talks with a nurses' union, officials at Washington Hospital Center will put a wage proposal into effect Friday that would pay nurses less for working evenings, nights and weekends, officials said.

The proposal will increase the base pay for most nurses by 4.5 to 6.75 percent over three years, but it will effectively cut the shift differential they earn for working evenings, nights and weekends. Those reductions amount to "wage cuts for everybody, really, except for a very, very few nurses," said Stephen Frum, chief shop steward for Nurses United of the National Capital Region, which represents the hospital's approximately 1,600 nurses.

He said the union is considering options and trying to determine whether the hospital's move is legal.

Janis Orlowski, the hospital's chief medical officer, said the hospital took the step after bargaining stalled at the end of July. The contract had expired in April but both sides extended it as talks continued.

"We feel we have essentially had no response from [the union] over the last two months," she said. "This has been a difficult decision."

Hospital officials said the move was needed for "organizational planning." Union leaders said the timing may have been prompted by a union vote this weekend on whether to join the national Nurses United union.

Even with the cuts to shift differentials, Orlowski said, the nurses are among the highest paid in the metropolitan area. In 2009, the average nurse at the hospital center earned about $93,000, she said.

Unlike many other area hospitals that pay a flat hourly rate for shift differential, the hospital center used a percentage of base pay to calculate how much extra nurses would receive for working evenings, nights and weekends. That will no longer be the case. Union officials say such a move will have a significant effect on take-home pay.

A nurse with two years' experience, working three 12-hour shifts rotating days and nights, would have a base pay of about $54,162 and would have earned an extra $8,000 for shift differentials under the old system. The same nurse, under the new plan, would earn $1,400 less, Frum said.

A nurse with 10 years' experience working two 12-hour shifts every weekend would receive a pay cut of about $6,700, Frum said.

Relations between nurses and management have been tense since earlier this year, when 18 nurses were fired after they did not show up for work during the February blizzards that shut down most of the Washington area. Nine of them were reinstated.